U.S. patent number 4,313,522 [Application Number 06/073,604] was granted by the patent office on 1982-02-02 for static pressure regain coupler for an air distribution system.
This patent grant is currently assigned to Mitco Corporation. Invention is credited to Dimiter Gorchev, Karl U. Ingard.
United States Patent |
4,313,522 |
Gorchev , et al. |
February 2, 1982 |
Static pressure regain coupler for an air distribution system
Abstract
A static pressure regain coupler for coupling an input duct and
the upstream end of a branch take-off device having a main duct and
one or more channel. The static pressure regain (SPR) coupler
includes an upstream end which has substantially the same
cross-section as the input duct. The SPR coupler also includes a
downstream end which has a first port having the same cross-section
as the main duct of the take-off device, and a second port having
substantially the same cross-section as the channels of the
take-off device. The SPR coupler is adapted to couple most of the
input airflow to the take-off main duct, and a minor portion of
that air flow to the take-off channels.
Inventors: |
Gorchev; Dimiter (Boston,
MA), Ingard; Karl U. (Kittery Point, ME) |
Assignee: |
Mitco Corporation (Somerville,
MA)
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Family
ID: |
26754674 |
Appl.
No.: |
06/073,604 |
Filed: |
September 10, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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944133 |
Sep 20, 1978 |
4182430 |
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Current U.S.
Class: |
181/224; 181/256;
181/268; 454/906 |
Current CPC
Class: |
F16L
55/033 (20130101); F24F 13/24 (20130101); Y10S
454/906 (20130101) |
Current International
Class: |
F16L
55/02 (20060101); F24F 13/00 (20060101); F24F
13/24 (20060101); F16L 55/033 (20060101); E04F
017/04 () |
Field of
Search: |
;181/224,256,268,275,282,239,218 ;98/4B,4C,4VM,DIG.10,38 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1683572 |
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Jul 1967 |
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DE |
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2266780 |
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Oct 1975 |
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FR |
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Primary Examiner: Hartary; Joseph W.
Assistant Examiner: Fuller; Benjamin R.
Attorney, Agent or Firm: Kenway & Jenney
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. patent
application Ser. No. 944,133, filed Sept. 20, 1978, now U.S. Pat.
No. 4,182,430. This application is also related to U.S. patent
application Ser. No. 073,603, filed on even data herewith, now
abandoned and which is a continuation-in-part of Ser. No. 944,133.
Claims
We claim:
1. Apparatus for coupling an airstream from an input duct to an
output duct and at least one associated channel, comprising:
A. an input port having a cross-section substantially the same as
the cross-section of said input duct and adapted to receive
substantially all the air in said airstream,
B. an output port having a cross-section including at least two
parts, the first of said parts having a substantially the same
cross-section at its downstream end as said output duct and the
second of said parts having substantially the same cross-section at
its downstream end as said associated channel, wherein said second
part is contiguous to said first part,
C. a first airflow guide having lateral side walls defining said
first part, said first airflow guide being adapted to pass a first
portion of said received air through said first part to said output
duct,
D. a second airflow guide having lateral side walls defining said
second part, said second airflow guide being adapted to pass a
second portion of said received air through said second part to
said associated channel.
2. Apparatus according to claim 1 wherein said first airflow guide
includes an inner section defining an airflow path between said
input port and said first output port, and
wherein said second airflow guide includes an outer section
defining a shell region adjacent to the exterior of said inner
section, and a channel means for defining an airflow path from the
interior of said inner section to said second output port.
3. Apparatus according to claim 2 wherein said channel means is a
porous acoustic material.
4. Apparatus for coupling an airstream from an end of an input duct
to an end of an output duct and at least one branch duct,
comprising:
A. a branch take-off and silencer means, including
i. an inner section having a cross-section substantially the same
as the cross-section of said output duct, said inner section being
adapted for coupling at one end to said end of said output
duct,
ii. an outer section disposed about at least a portion of said
inner section and defining a shell region between said inner
section portion and said outer section,
iii. channel means for establishing at least one channel in said
shell region, said channel extending from a point near the end of
said shell region adjacent to said input duct to said end of said
branch duct, and
B. coupling means, including
i. an input port having a cross-section substantially the same as
the cross-section of said input duct, and adapted to receive
substantially all the air in said airstream,
ii. an output port having a cross-section including at least two
parts, the first of said parts having substantially the same
cross-section at its downstream end as said output duct and the
second of said parts having substantially the same cross-section at
its downstream end as said associated channel, wherein said second
part is contiguous to said first part,
iii. a first airflow guide having lateral sidewalls defining said
first part, said first airflow guide being adapted to pass a first
portion of said received air through said first part to said output
duct,
iv. a second airflow guide having lateral sidewalls defining said
second part, said second airflow being adapted to pass a second
portion of said received air through said second part to said
associated channel.
5. Apparatus according to claim 4 wherein said first airflow guide
includes an inner section defining an airflow path between said
input port and said first output port, and
wherein said second airflow guide includes an outer section
defining a shell region adjacent to the exterior of said inner
section, and a channel means for defining an airflow path from the
interior of said inner section two said second output port.
6. Apparatus according to claim 5 wherein said channel means is a
porous acoustic material.
7. Apparatus for coupling an airstream from an end of an input duct
to an end of an output duct and at least one branch duct,
comprising:
A. an inner section having a cross-section substantially the same
as the cross-section of said output duct, said inner section being
adapted for coupling at one end to said end of said output
duct,
B. an outer section disposed about at least a portion of said inner
section and defining a shell region between said inner section
portion and said outer section,
C. channel means for establishing at least one channel in said
shell region, said channel extending from a point near the end of
said shell region adjacent to said input duct to said end of said
branch duct.
8. Apparatus according to claim 7 wherein said input and output
ducts have circular cross-sections at said ends to be coupled,
whereby said channel has a curved central axis extending from its
input end near said input duct to its output end near said branch
duct, said central axis being parallel to said input duct central
axis at the input end of said channel, and being parallel to said
branch duct central axis at the output end of said channel.
9. Apparatus according to claims 7 or 8 wherein said channel means
comprises a sound absorbing element disposed within said shell
region.
10. Apparatus according to claim 8 wherein said input and output
ducts have polygonal cross-sections at said ends to be coupled.
11. Apparatus according to claim 10 wherein said shell region is
established between one pair of parallel planar faces of said inner
and outer sections.
Description
BACKGROUND OF THE INVENTION
This invention relates to air distribution systems and more
particularly to apparatus for extracting air from a main supply
duct to a branch duct.
In a conventional air distribution system in a building, the air is
branched from the main air supply duct to the various branch ducts
through openings in the wall of the main duct which enter into the
branch ducts.
Generally, the volume flow rate through the branch is determined by
the static pressure in the main duct and the flow resistance of the
branch. Since the branch opening is flush with the wall of the main
duct, the dynamic pressure of the flow in the main duct does not
contribute to the flow rate in the branch.
In such configurations, the noise level at the entrance to the
branch duct is substantially the same as the noise level in the
main duct. This level is generated mainly by the air supply fan,
which noise travels through the main air duct without much
attenuation. In the prior art, to reduce the noise level, a
silencer is typically used at the exit of the fan in the main
supply duct. Frequently a silencer is also incorporated at the
inlet to the main supply fan.
In order to minimize the effects of the silencer on the system, the
silencer must have a low pressure drop and its total open area must
be large. Thus, if adequate acoustic attenuation is to be achieved,
the silencer dimensions must be made quite large. This means that
the silencer has the disadvantage, not only of being costly, but
also bulky, requiring a large amount of space. If the dimensions of
the silencer are reduced, the pressure drop will increase and it
may then be necessary to select a larger fan to achieve the
required total volume flow rate through the main duct. This latter
alternative is extremely costly from an energy standpoint.
In order to further attack the noise problem, silencers may be
introduced in the branch ducts, or alternatively, the branch ducts
may incorporate noise attenuating liners. It should be kept in
mind, however, that in order for such a silencer or liner to be
effective at low frequencies, the absorptive elements must be quite
thick, and in order for the pressure drop in the branches to be
kept to an appropriately low value, the dimensions must be
correspondingly large. This leads to impractical distribution
systems.
It is an object of the present invention to provide a static
pressure regain coupler for use with a branch take-off and
silencer.
It is a further object to provide a composite branch duct take-off
and silencer having a static pressure regain coupler.
It is another object to provide a composite branch take-off and
silencer and associated static pressure regain coupler, eliminating
the need for a silencer at the fan.
Yet another object is to provide a composite branch take-off and
silencer and associate static pressure regain coupler providing
relatively high air handling capacity and the volume flow in a
branch duct.
SUMMARY OF THE INVENTION
Briefly, the present invention is a composite branch take-off and
silencer for an air distribution system wherein an airstream from
an input duct may be coupled to an output duct and one or more
branch ducts. Inner and outer sections define a shell region. The
shell region is closed at its downstream end and is adapted at its
upstream end to receive oncoming air from the input duct. Porous
acoustical material is positioned within the shell region to
establish one or more channels in that region which extend from the
upstream end to points adjacent to one or more of the branch ducts.
At these points, the channels are coupled to one or more of the
branch ducts. The downstream end of the inner section is coupled to
the output duct.
A static pressure regain coupler provides coupling between the
input duct and the upstream end of the branch take-off and silencer
(TO/S) device. The static pressure regain (SPR) coupler includes an
upstream end which has substantially the same cross-section as the
input duct. The SPR coupler also includes a downstream end which
has a first port having the same cross-section as the TO/S inner
section, and a second port having substantially the same
cross-section as the shell region channels of the TO/S device. The
SPR coupler is adapted to couple most of the input airflow to the
TO/S inner section, and a minor portion of that air flow to the
TO/S channels. The static pressure regain coupler may be a discrete
element for coupling between the input duct and the TO device, or
it may be integral with the TO device. With this configuration, the
airflow velocity decreases as the flow passes from the input duct
to the output duct, resulting in a static pressure gain.
BRIEF DESCRIPTION OF THE DRAWING
The foregoing and other objects of this invention, the various
features thereof, as well as the invention itself, may be more
fully understood from the following description when read together
with the accompanying drawing in which:
FIG. 1 shows a sectional view of an embodiment of the present
invention;
FIGS. 2-4 show sectional views of the embodiment of FIG. 1;
FIGS. 3 and 4 show sectional views of an alternative embodiment of
the present invention;
FIGS. 5-9 show sectional views of other embodiments of the present
invention;
FIGS. 10 and 11 show perspective views of additional embodiments of
the present invention; and
FIGS. 12 and 13 show perspective views of exemplary static pressure
regain couplers adapted for use with the embodiment of FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an examplary branch take-off and silencer for air
distribution system having an input duct 10, an output duct 12 and
a branch duct 14. Airflow through the apparatus of FIG. 1 is
indicated by the arrows A, B and C in that figure. FIGS. 2, 3 show
sectional views of the elements of FIG. 1. The elements in FIGS.
2-4 which correspond to elements in FIG. 1 are identified by
identical reference numerals.
Ducts 10 and 12 have similar, i.e. same shape, cross-sections. In
this example, cross-sections are circular, with the input duct
having a relatively large cross-section compared with the output
duct. The ducts 10 and 12 are substantially coaxial at the ends to
be coupled. In the illustrated embodiment, ducts 10 and 12 overlap.
The overlapping portion of duct 10 is referred to hereinafter as
the outer section 20 of the invention. The overlapped portion of
duct 12 is referred to hereinafter as the inner section 22 of the
invention. In the present embodiment, inner and outer sections 20
and 22 are formed by extensions of the respective ducts 10 and 12.
In alternative embodiments, sections 20 and 22 may be separate from
the ducts 10 and 12 but joined to the respective ducts at the point
of overlap.
The shell region between the sections 20 and 22 is referred to
generally by reference designation 24 in FIG. 1. In the present
embodiment, the shell region 24 is annular. An annular plug 26
provides a seal to the shell region at the downstream end of that
region. Plug 26 is a porous acoustical material such as glass
wool.
The annular shell region 24 is open at its upstream end to be
oncoming airflow in the input duct 10 (indicated by arrow A). The
airflow in the shell region 24 exits to the branch duct 14 near the
downstream end of region 24. In the illustrated embodiment, the
annular region 24 is divided into three adjacent channels which are
separated by elongated partitions 32, 34 and 35 of porous
acoustical material, such as glass wool. In FIG. 1, only two
partitions denoted 32 and 34 are shown, although all three may be
seen in FIG. 2. The partitions are generally tapered from upstream
to downstream end and have a dimension equal to the radicl distance
between sections 20 and 22 in the radial direction. The channels
extend from a point near the upstream end of sections 20 and 22 to
an intermediate point denoted by their reference designation X in
FIG. 1 in the region 24. Beyond the channels in region 24 is a
substantially annular common plenum 36 which is coupled to the
branch duct by means of a butt joint 38.
Each channel acts like an acoustically lined duct, with two
opposite sides lined. Since the porous partitions in the annular
region 24 can be made quite thick, such as eight inches in typical
thirty-six inch diameter duct, the attenuation of the device can be
more than adequate throughout the entire frequency range of
interest. Thus, the resultant attenuation is comparable to that of
a large fan silencer. Unlike the fan silencer, however, the present
invention can be increased in length without the need for
additional space.
The frequency dependence of the acoustic attenuation of the device
may readily be adjusted by variations in the width of the channels
(i.e. the distance between the two porous walls in the channel),
and the thickness and number of the porous partitions in the
annular section. The density of the porous material is also a
parameter which can be chosen independently of the others. In the
preferred embodiment, the density is selected such that the
acoustic flow resistance per inch of the material is between 50 and
10 CGG units, generally corresponding to a density of about six
pounds per cubic foot. The required length, L, for the channel is
less than 1/3 of the product of the width of the channel, W, and
the desired attenuation, A. The details of the frequency dependence
of the attenuation may be determined from well-known procedures for
lined ducts.
In the illustrated embodiment, the channels in through section 24
are relatively straight. In response to airflow A, a relatively
high static pressure is built up in region 36, with this high
static pressure driving airflow into the branch duct to form a
branch airflow denoted by reference designation C. The remaining
portion of the main airflow exits into the output duct and is
denoted in FIG. 1 by reference designation B.
FIGS. 5-6 and FIGS. 7-9 illustrate further embodiments of the
present invention. In those figures, elements corresponding to
similar elements in the embodiment of FIGS. 1-4 are identified with
the same reference designations. FIGS. 5 and 6, show a form of the
invention suitable for coupling rectangular input and outputs
ducts. In still other embodiments, ducts may have alternative
polygonal cross-section shapes.
In the embodiment of FIGS. 5 and 6, the channel forming members
42A-42F are substantially the same shape as the corresponding
member 32 in the above-described embodiment, except the top and
bottom surfaces are planar for members 42A-42F in order to provide
a flush fit with the inner and outer surfaces of sections 20 and
22, respectively. In FIGS. 5-6, there are four corner channel
forming members 44A-44D which extend to the point X as to the
members 42A-42F, with the members 44A-44D forming broadening
channels for airflow in the shell region 24. The plug 26 has
rectangular inner and outer surfaces to provide a seal at the end
of the overlapping portions of inner and outer sections 20 and
22.
In operation, the embodiment of FIGS. 5 and 6 operates
substantially in the same manner as the embodiment of FIGS. 1-4,
with a static pressure build-up in plenum 36 driving airflow tapped
from the main stream into the branch duct 14. Similarly, the
remaining portion of the main stream is represented by flow arrow B
into the output duct 12.
The embodiment of FIGS. 7-9 illustrates another embodiment suitable
for coupling an airstream in an input duct 10 (represented by arrow
A) to a branch duct 14 (arrow C) with the remainder of the airsteam
continuing to the output duct 12 (arrow B).
This latter embodiment is substantially similar to that in FIGS.
1-4 except that the partitions 52, 54 and 56 are adapted to form
channels in the shell region 24 having substantially helical
central axes extending from the portion of the shell region
adjacent to input duct 10 to the intermediate point X. At the point
X, the central axes of these channels are substantially parallel to
a plane passing through point X and being perpendicular to the
common axis of sections 20 and 22. Thus, in this embodiment, the
channel axes are generally helical with a pitch varying from
infinite at the input and to zero at the output end.
With this configuration, air tapped from the input duct 10 and
passing through the shell region 24 is directed to flow
circumferentially in the plenum 36 (in the counter-clockwise
direction viewed from duct 10 in the embodiment of FIGS. 7-9). A
junction 60 is provided to tap off the airflow from the flow
direction in plenum 36 and couple that airflow to the branch duct
14. For this junction, conventional techniques may be utilized,
such as those found in centrifugal fans, for example. In this
embodiment, the velocity pressure of the airstream moving in the
direction flow of plenum 36 drives the tapped air through junction
60 to the branch duct 14. In alternative embodiments, the junction
section 60 may provide fully tangential take-off of the air-flow
from the plenum. In such embodiments the outer wall 61 of section
60 is substantially planar and is tangent to the section 20 where
joining that section.
In all the above embodiments, only a single branch duct 14 is
illustrated, although in other embodiments, additional branch ducts
may be incorporated similarly.
In the illustrated embodiments, the partitions forming the channels
are tapered, and provide widening channels in the straight channel
embodiments, and substantially uniform width channels in the
helical embodiments. In alternative embodiments, the partitions in
the shell region may establish the channels having substantially
uniform width. In such cases, in helical channel embodiments, the
channels are tapered, while in the straight channel embodiments the
channels are uniform width.
FIGS. 10 and 11 show other alternative configurations adapted for
coupling an input duct with an output duct and a single branch
duct. In those figures, elements having corresponding elements in
the configurations of FIGS. 1-9 are identified by the same
reference designations.
In FIG. 10, a branch take-off and silencer device is shown with a
similar cross-section inner section 22 and outer section 20
defining a shell region 24. The sections 20 and 22 are
substantially coaxial. In this embodiment, section 22 is formed by
an extension of the output duct. In alternative forms, section 22
may be separate from the output duct but joined at the downstream
end to that duct.
In the illustrated embodiment, a single airflow channel 60 is
established in the shell region 24 by a partition member 62 which
fills the shell region 24, except for the channel 60. The partition
member 62 is preferably a porous acoustical material, such as glass
wool. This channel is adapted at its upstream end to receive a
portion of the oncoming airflow (indicated by arrow A) in the input
duct 10 (not shown). This portion of the airflow in the shell
region 24 passes along the longitudinal, or central, axis of
channel 60 and exits to the branch duct 14 near the downstream end
of region 24.
In the present embodiment, at the upstream end of channel 60, that
channel's central axis is parallel to the central axis of input
duct 10, and at the downstream end of channel 60, that channel's
central axis is parallel to the central axis of branch duct 14. In
FIG. 10, only one channel is established for coupling to the single
duct 14, although additional channels may similarly be coupled to
additional output ducts in other embodiments. In alternate
embodiments, a rectangular-to-circular cross-section converter may
be used to match the rectangular channel 60 to a circular branch
duct.
The configuration of FIG. 11 is particularly adapted for a
rectangular cross-section output duct. As shown in FIG. 11, the
output duct 12 includes a rectangular cross-section extension
section 22. A rectangular cross-section outer section 20 overlaps
the extension section 22. The dimensions of these sections 20 and
22 are adapted so that section 22 fits snugly within section 20
along three sides and provides a shell region 24 along the fourth
side. A single airflow channel 70 is established in the shell
region 24 by partition members 72 and 74. Preferably members 72 and
74 are formed from a porous acoustic material. The channel 70 is
adapted to receive a portion of the oncoming airflow (indicated by
arrow A) in the input duct 10 (now shown). This portion of the
airflow in the shell region 24 exits to the branch duct 14 near the
downstream end of region 24. In alternate forms, additional
channels may be established in region 24, or in additional similar
regions which may be similarly formed along other sides of the
overlapping sections 20 and 22. In addition, this form of the
invention may be used with other overlapping polygonal
cross-section sections, where the shell region is established
between one pair of planar faces of the inner and outer sections.
In still other embodiments, additional channels which lead to
additional branch ducts may be established in that shell region or
in similar shell regions between additional pairs of planar faces
of the inner and outer sections.
Although the present embodiments have been described in terms of
overlapping input and output ducts, functionally equivalent
interface ducts may be used to couple those input and output ducts.
In addition, while rectangular and circular cross-section ducts
have been described, it will be understood that other cross-section
shapes may similarly be utilized within the scope of the invention.
For example, overlapping elliptical ducts may be used in one such
form.
The take-off and silencer (TO/S) devices shown in FIGS. 10 and 11
may be used in one form where the input duct 10 has substantially
the same cross-section as the upstream end of outer section 24. In
another form, the TO/S device of FIG. 10 may be used in accordance
with the present invention with a static pressure regain (SPR)
coupler between the input duct 10 and the upstream end of the TO/S
device. The latter form is particularly advantageous where the
input duct 10 and output duct 12 have substantially the same
cross-sections.
In this form, the SPR coupler defines an airflow port at its
upstream end having substantially the same cross-section as the
TO/S inner section 22. This end of the SPR coupler is directly
coupled to the input duct 10. In addition, the SPR coupler defines
an airflow port at its downstream end which has substantially the
same cross-section as the TO/S inner section and in addition
includes a port extending from a channel from the interior of the
SPR coupler inner section. This latter port is adapted to couple to
one or more of the channels in the TO/S shell region. The SPR
coupler may be a discrete element or may be intergral with the TO/S
device. With this configuration, the airflow velocity decreases as
the flow passes from the input duct to the output duct resulting in
a static pressure gain along that path. A relatively minor portion
of the flow from the input duct is tapped off to the channels
leading to the branch ducts.
FIG. 12 shows an exemplary SPR coupler 80 for use at the input end
of the TO/S configuration of FIG. 11. That exemplary device 80
includes a rectangular port 82 at its upstream end for coupling to
rectangular input duct 10, a rectangular port 84 for coupling to
inner section 22, and a rectangular port 86 for coupling to channel
70. As shown, port 86 terminates an airflow guide (or channel) 88
formed by the walls of the top portion of coupler 80 which bound
that channel adapted to pass a relatively small portion of the
input airflow (at port 82) to channel 70 of the take-off/silencer
device of FIG. 11, thereby establishing the flow denoted "C" in
that figure. Port 84 terminates an airflow guide (formed by the
side, top and bottom walls of SPR coupler 80, and channel 88)
adapted to run a relatively large portion of the input air flow (at
port 82) to the main duct portion of the take-off/silencer of FIG.
11, thereby establishing the flow denoted "B" in that figure. In
the illustrated form, the channel 88 is formed by the upper (as
shown) surface of the device 80. FIG. 13 shows an alternative form
of device 80, having a similar channel 88 established by acoustic
materials 92 which may be positioned within a shell region 96
(similar to region 24 in the TO/S device) established by housing
member 98.
In various applications, the SPR coupler may be utilized
immediately adjacent to the upstream end of a TO/S device, as
suggested above in conjunction with FIGS. 11 and 12. Alternatively,
the SPR coupler may be coupled to the upstream end of a TO/S by an
extended coupling duct. In the latter form, a number of TO/S
devices may be deployed in series, with the downstream end of each
such device being directly coupled to the SPR coupler for the next
TO/S device, which in turn is coupled to that TO/S device by such
an extended duct.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *